File Input and Grading script

I'm new to Matlab. I'm trying to learn some basic functions. I want to import a file with grades. After sanity checks, I want to strip off the lowest score, then average it. Then plot this. Is this a best practice method below?

    function grades = loadData(filename, checkErrors)
    % function takes a grades-csv and TRUE/FALSE to check for errors.
    % if check ERROR true, finds errors in data and prints.
    % returns a grades matrix grades.

        GRADE_SCALE = [12 10 7 4 0 2 -3];

    input      = importdata(filename, ',');
    grades     = input.data;
    studentIDs = input.textdata(2:end,1);
    nStudents  = size(grades,1);
    nAssigns   = size(grades,2);

    if (checkErrors==true)
    %error checking - student IDs
    [~, index] = unique(studentIDs);
    notUniqueIDs = studentIDs;
    notUniqueIDs(index) = [];

    for i = 1:length(notUniqueIDs)
    fprintf('Duplicate student ID %s.\n',notUniqueIDs{i});
    end
    %error checking - student grades
    for i = 1:nStudents
    for j = 1:nAssigns
    if ~ismember(grades(i,j),GRADE_SCALE)
    fprintf('Invalid Grade for Student %s, Assignment %d.\n', studentIDs{i}, j);
    end
    end
    end
    end
    end

    function gradesRounded = roundGrade(grades)

    gradesRounded = [];
    for i=1:length(grades)
      if grades[i]<-1.5
        gradesRounded[i] = -3;
      if grades[i]>=-1.5  && grades[i]<1
        gradesRounded[i] = 0;
      if grades[i]>=1  && grades[i]<3
        gradesRounded[i] = 2;
      if grades[i]>=3  && grades[i]<5.5
        gradesRounded[i] = 4;
      if grades[i]>=5.5  && grades[i]<8.5
        gradesRounded[i] = 7;
      if grades[i]>=8.5  && grades[i]<11
        gradesRounded[i] = 10;
      if grades[i]>=11
        gradesRounded[i] = 12;
    end

    end

    % Take minimum value of each row in the matrix
    function gradesFinal = computeFinalGrades(grades)
    B = zeros( size(grades,1)-1, size(grades,2));
    for i=1:size(grades,2)
    x = grades(:,i);
    maxIndex = find(x==min(x(:)),1,'first');
    x(maxIndex) = [];
    B(:,i) = x;
    end

    % Get average grade
    average_grades = mean(B,2);

    rows = Size(grades,1);
    cols = Size(grades,2);
    for i = 1:rows
      for j=1:cols

      end
    end

    end

    function gradesPlot(grades)
      bar(grades[0],grades[1]);
      set(gca,'xticklabel',{'a','b','c','d','e','f','g','h','i','j','k','l'});
      title('Student Rounded Grade Plots');
      xlabel('Assignments');
      ylabel('Grades');
      legend('x = Assignments','y = Grades','Location','southwest');
    end

    % main program

    % read input file
    g = loadData(filename,true);
    % get rounded grades
    grades = roundGrade(g);

    % final grades
    grades2 = computeFinalGrades(grades);

    % Plot Grades
    gradesPlot(grades2);

[dpb]

One of your classmates has already been here. I gave him some hints at

http://www.mathworks.com/matlabcentral/answers/170568-i-need-help-with-a-matrix-input-and-a-vector-output-please

[dpb]

The routines I wrote...

>> type computeGrades

function finalgrade=computeGrades(grades)
  if size(grades,1)==1        % if only one exam, grade is that
    finalgrade=grades;
    return
  end
  % at least two scores and more...
  isThree=any(grades==-3,2);  % who got a -3?
  finalgrade(isThree)=-3;     % no 2nd chance for them, apparently...
  grades=sort(grades(~isThree,:),2);  % those w/o a -3 to average
  grades=grades(:,2:end);             % and toss the lowest score
  finalgrade(~isThree)=roundGrade(mean(grades,2)); % their ending avg
  finalgrade=finalgrade(:);           % return a column vector

>> type roundGrade

function avgGrade=roundGrade(grades)
  values=[-3, 0, 2, 4, 7, 10, 12].';  % the allowable levels
  avgGrade= interp1(values,values,grades,'nearest');

>>

It's unlikely these will directly help in an intro course (at least without a lot of 'splaining :) ) but I'll post them as a demo of "the Matlab way" to use the vector facility of Matlab to avoid looping and the succinctness possible via some of the supplied functionality. You just have to have had "time in grade" to think of things like interp1 for the rounding. There are any number of other ways, I chose this simply as a demo of the specific feature of 'nearest' lookup being "cute".

I pushed the other poster to try to think of the logical array and all, but it's an admitted stretch for a new initiate...